Ovalicin is a metabolite of Pseudorotium ovalis possessing antibiotic, antitumor, immunosuppressive, and seed germination stimulating properties. Fomannosin is a phytotoxic metabolite of the economically important wood-rot fungus Fomes annosus. The structure of each of these sesquiterpenes presents a unique and complex biosynthetic problem, not readily amenable to traditional labeling and degradation techniques. The research project involves the application of a powerful instrumental technique carbon magnetic resonance, to the solution of the biosynthetic problems posed by these substances. The goal is 1) to elucidate the rearrangement pathway by which ovalicin is formed; 2) to establish a biosynthetic scheme for the formation of fomannosin and to provide mechanistic and stereochemical details bearing on that scheme; and 3) to probe and extend the utility of homo- and heteronuclear double labeling in CMR studies of natural product biosynthesis. BIBLIOGRAPHIC REFERENCES: David E. Cane and Ronald H. Levin, "Application of Carbon-13 Magnetic Resonance to Isoprenoid Biosynthesis. II. Ovalicin and the Use of Doubly-Labeled Mevalonate", J. Am. Chem. Soc., 98, 1183 (1976). David E. Cane and Robert B. Nachbar, "Biosynthesis of Fomannosin from 1,2-13C-Acetate," Tetrahedron Lett., (1976), in press.